Graft Detachment After Descemet's Stripping Automated Endothelial Keratoplasty in Bullous Keratopathy and Fuchs Dystrophy.

Descemet’s stripping automated endothelial keratoplasty (DSAEK) is a surgical technique for corneal transplantation in case of corneal decompensation. One of the main complications is graft detachment (GD) recoverable with Air Re-bubbling (ARB). The aim of this retrospective, interventional case series was to identify factors related to this complication in eyes operated for bullous keratopathy (BK) and Fuchs dystrophy (FD). We considered one-hundred patients who underwent DSAEK for BK or FD between January 2016 and October 2017 at Department of Ophthalmology, Policlinico Universitario of Bari, Italy. Studied parameters included physiological and pathological anamnesis of both donors and recipients and properties of donor’s lenticules and of the recipient’s corneas. Data was analyzed using One-way ANOVA with Tukey post hoc test and Chi-square test with Odds Ratio (OR) calculation. We grouped patients according to diagnosis. GD occurred in 9 eyes affected by BK and 19 by FD (p=0.003, OR = 0.25, 95% CI, 0.098-0.62). It was recovered with ARB. In BK, ARB correlated to complicated cataract extraction (p=0.04, OR = 7.83, 95% CI, 1.28 – 47.98) and aphakia (p=0.026, OR = 54.38, 95% CI, 2.51 - 11.76). In FD, ARB was associated to donor’s death for neoplasia (p=0.06, OR= 4.04, 95% CI, 1.06 – 15.37). No other differences were found. In conclusion, we could hypothesize that in FD patients, donor’s cancer therapy may play a role on altered corneal fibroblast metabolism, activating a synergetic effect between chemotherapy and genetic alteration of FD, which may lead to an altered adhesion of donor’s lenticule on recipient's stroma. In BK patients, complicated cataract extraction and aphakic status of recipients’ eye may contribute to altered adhesion of donor’s lenticule post-DSAEK.


INTRODUCTION
Bullous keratopathy (BK) and Fuchs dystrophy (FD) are among the most common causes of corneal decompensation, often requiring corneal transplantation [1]. BK is a complication of many types of eye surgery, especially cataract extraction. It is characterized by corneal edema and stromal bubbles which cause pain and visual impairment [2]. Fuchs dystrophy is a bilateral corneal disease [3] due to an altered expression of the corneal endothelium-specific type VIII collagen [4,5], which leads to a progressive deterioration of the endothelium. In earlier stages, it is characterized by 'guttae', anatomic alteration of the Descemet's membrane, visible as dark areas under the specular microscope. In the following stages, the confluence of GRAFT DETACHMENT AFTER DESAEK the guttae, progressive endothelial cell loss and impairment of their stromal drainage lead to stromal and epithelial edema with micro-and macrobubbles, associated with decreased visual acuity and pain [2,3,5]. In both cases, the gold standard of treatment is Descemet's stripping automated endothelial keratoplasty (DSAEK) [6][7][8]. Surgical complications occur in about 14% of cases and the most common one is graft detachment (GD), which occurs within the first days or up to six postoperative weeks [9,10]. GD needs additional surgical treatment with surgical related risks. Air Re-Bubbling (ARB) is usually performed by inflating the anterior chamber with air to reattach corneal flap to the recipient's stroma [11]. In this study we aimed to identify factors related to GD after DSAEK in eyes operated for BK and FD, focusing on donors and recipient's corneas properties and their medical history.

METHODS
In 2017, ethical committee approval for retrospective studies was not required by Policlinico Universitario of Bari. In our Department level, a generic scientific informed consent was obtained from all patients before surgery. This study was performed in compliance with the principles of the Declaration of Helsinki. We made a retrospective analysis of 59 eyes affected by BK and 45 eyes with FD undergoing DSAEK between January 2016 and October 2017 at the Eye Clinic, Department of Ophthalmology of the University General Hospital of Bari, Italy. Patients were identified by searching the Cornea Service of Bari Eye Clinic database. Data was collected including patient's gender and age, corneal decompensation period, presence of pseudophakia, other ocular pathologies, keratometry (steep axis and average keratometry), pachymetry and possible concurrent phacoemulsification. Moreover, we analyzed data about thickness, endothelial cell density and diameter of the corneal lenticule as well as eye bank origin, donor's gender and age, death cause and time span between death and corneal explantation. Finally, the occurrence of ARB, potentially repeated, was recorded. DSAEK was performed according to the standardized techniques [12], namely making a small corneal incision, stripping the Descemet's membrane and endothelium layer, injecting the donor's lenticule and positioning it with an air bubble in the anterior chamber. Pupillary block was prevented thanks to an inferior iridectomy. Then the patient was instructed to lay in a supine position in the following four hours. Anterior segment biomicroscopy and anterior segment optical coherence tomography (AS-OCT) were performed 1.5 and 12 days after the operation. AS-OCT (MS-39, CSO srl, Scandicci (FI), Italy) investigated the presence of fluid between the donor's lenticule and patient's stroma by means of two-dimension 24 radial lines centered on corneal apex (16 millimeters [mm] length) [13]. GD was characterized by the presence of fluid between the transplanted lenticule and the recipient cornea (Figure 1). It was immediately treated by introducing an air bubble in the anterior chamber called ARB and spreading out the lenticule to attach it to the recipient's underlying layers ( Figures. 2 and 3).

DISCUSSION
Statistical analysis of early GD rate in our study establishes the need of post-DSAEK ARB in about 28% of treated eyes, 16.4% of BK and 42.2% of FD. This finding confirms the literature data reporting mean GD rate as 14% [9,10], or in a range of 4-27% [11,14]. Focusing on BK group, our data confirmed a higher risk of GD in case of aphakia or in complicated cataract extraction. In literature the role of glaucoma in GD is controversial [15][16][17][18]. As recorded in recent studies by Pavlovic et al. [17], our data do not correlate GD to glaucoma both in BK and FD. Other investigated parameters (Tables 4, 5) did not correlate with GD in both groups, except for lenticules, explanted from patients affected by neoplasia, in FD where ARB was more frequent (42.2%) than in BK (15.2%). Demsey [19] demonstrated that graft dislocation is not influenced by variation in donor tissue processing and storage times. This evidence was extended to precut Eye Bank tissue thanks to Dapena et al. [14]. We excluded the influence on GD of time lapse between donor death and tissue implantation. A histopathological study of detached and failed graft conducted by Alkatan et Al., reported a higher risk of GD in case of irregular or thick graft, graft-host interface fibrous/epithelial ingrowth and interface infection [20]. Due to retrospective limitation of our study we could consider only the thickness of lenticules, as recorded by Eye Bank data forms. For both groups thickness of lenticules was similar, avoiding any interference related to tissue preparation. Moreover, ARB was successful and recovered GD in all cases, excluding any further postoperative analysis. We did not perform venting incision to prevent any postoperative complication in patients discharged the day after surgery. Even if venting incisions could improve the adherence of donor's lenticule [21], it might increase the risk of deep infectious keratitis [22] or induce corneal irregular astigmatism [23]. Mohebbi assumed that venting incision may not be necessary in the standard DSAEK procedures [24] we refrain to proceed with this technique. Anterior segment biomicroscopy did not reveal any sign of graft failure or graft rejection prior or after ARB [25,26].    The exclusion of those risk factors in FD enhanced the correlation between lenticules explanted from patients affected by neoplasia and GD. This evidence points toward a causative relationship between the FD physiopathology and GD. Assuming that we did not find historical evidence of congenital corneal disorder, FD is an autosomal dominant disease that affects deeper corneal layers collagen [27] that are partially stripped in DSAEK and partially prepared to attach to graft. DSAEK technique realizes the stripping of the Descemet-Endothelium complex. Probably the deeper stroma next to Descemet's membrane is the weak link in graft adhesion, due to its anatomical and functional damage [28,29]. Many reports have studied the effect of chemotherapy for different type of cancer on systemic tissues, especially on connective layers, inducing jeopardized disorders [30][31][32][33]. Along this evidence we suppose that chemotherapy affects donor's corneal stroma, interfering with fibroblastic metabolism [34]. This feature is not relevant in BK but could be critical on corneas affected by congenital and metabolic disorders as in FD, increasing the risk of GD [3,35,36]. Due to our limited access to donors' clinical history, we do not have any data about neither donors' neoplasia nor related chemotherapy. Strengths of the study included homogeneous sample and experienced single-surgeon (G.A.). Our data are limited by the retrospective design of the study. We considered ARB and anatomical recovery of GD in BK and FD. Histopathologic examination of donor's detached lenticule was not performed because in all eyes GD was totally recovered by ARB. Long-term postoperative functional and anatomical evaluation was not recorded because patients were discharged immediately after surgery and followed by territorial ophthalmic offices. Therefore, future studies by eliminating these limitations could be more informative and valuable.

CONCLUSIONS
Although this study showed a complete and easy graft reattachment with ARB, it might expose patients to further risks. A desirable outcome would be identification of the risk factors of GD to limit further surgical approaches. We found that, as widely reported in the literature, aphakia and complicated cataract extraction increase the risk of GD in BK. To our knowledge for the first time we identified that graft explanted from neoplastic donor may impair DSAEK in FD, increasing GD rate of 2.6.

DISCLOSURE
Ethical issues have been completely observed by the authors. All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship of this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval for the version to be published. No conflict of interest has been presented. Funding/Support: None. The datasets analyzed during this study are available from the corresponding author on reasonable request.